1. Field of the Invention
The invention relates to a pressure vessel, in particular for a vibration damper, filled with a medium and having a variable-shape envelope containing a mass of gas for volume compensation.
2. Description of the Related Art
U.S. Pat. No. 6,116,585 discloses a pressure vessel which is filled with at least one medium which is prestressed by a mass of gas which is enclosed in a variable-shape envelope, in particular for volume compensation in a vibration damper, having a wall in which a pressurized gas is enclosed. The wall of the envelope is at least partially formed from a barrier layer and the envelope being composed of a plurality of individual parts.
On account of the gastight barrier layer, the emergence of gas from the pressure vessel is considerably improved compared to simple pressure vessels with a rubber membrane. Nevertheless, over the intended service life, it is possible to detect a loss of gas from the pressure vessel, and the aim is for this loss to be reduced further. One procedure consists in the use of a plurality of gastight barrier layers. Alternatively, the barrier layers may be designed with a protective layer which can withstand particularly high thermal loads. Extensive tests have shown that the temperature at which the pressure vessel is used has a decisive effect on the seal. However, heat-resistant protective layers of this nature are relatively expensive, and consequently they tend not to be suitable for large-series production.
It is an object of the present invention to minimize the problems which are known from the prior art and are caused by the loss of gas from the pressure vessel.
According to the invention, the object is achieved by providing an outside coating, which seals an end face of the envelope, at least at an edge-side contact region of the individual parts of the envelope.
The envelope is formed by at least two individual parts which are welded together. The previous weak point of the edges at which the gastight barrier layer is only in superficial contact is significantly improved by the additional coating.
To achieve the maximum possible compatibility of the outside coating, with the envelope comprising a plurality of layers, the material for the coating of the end face is similar to the outside layer of the envelope.
With a view to saving on use of raw materials, but also to keeping the envelope as flexible as possible, the edge-side coating is restricted to a strip of xe2x89xa65 mm.
In connection with this measure, the envelope has a prestamped form which is adapted to the intended installation position, the coating being made on the prestamped envelope. The stresses which occur within the coatings can be significantly reduced.
In a further advantageous configuration, the envelope has an injection-molded filling connection.
In order to ensure that there are no additional leakage points, the filling connection is arranged in the edge region. For this purpose, the filling connection has a conical contact region, on which in each case a section of the edges of the envelope comes to bear.
In a further advantageous configuration, the edge-side coating is connected to the filling connection.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.